1. Field of the Invention
The present invention relates to a data-processing system having an address bus and a data bus to which are connected a central processing unit, main memories, and control circuits for peripheral equipment.
2. Background Information
Conventional data-processing systems, such as personal computers, are not protected from unauthorized access to the central processing unit (CPU). From terminals or other communications interfaces, for example, programs can be started in the CPU which can both change user programs in the main memory and destroy programs and data in peripheral bulk storages.